The invention relates to sulfonium electrophilic alkylating reagent of formula I, wherein is an aryl group, R2 is an alkyl group, R3 is a substituted Ph group, wherein the no. of substituents (n) is greater than 2 and R4 is an anion, and salts thereof, methods for their prepn. and methods for the prepn. of a wide variety of alkylated biol. active compds. using such reagents. Example compd. II was prepd. by reacting Me Ph sulfoxide (prepn. shown) with 1,2,3,4-tetramethylbenzene in the presence of trifluoromethanesulfonic anhydride in 94% yield as a white solid. Example compd. II was then used for prepn. of (10R,13S,17R)-Me 11,17-dihydroxy-10,13-dimethyl-3-oxo-6,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a]phenanthrene-17-carboxylate by methylation of the corresponding carboxylic acid in the presence of Cs2O3 in dichloromethane at room temp. Tiotropium bromide (III) was prepd. similarly.